The history of the USSR during these years must be redone again from the beginning. Here's a list of just a few of the cardinal events in this history that are either largely or completely distorted in anticommunist historiography (including the anticommunist historiography in Russia itself):

The so-called "man-made famine in Ukraine" is a myth. It was not "man-made" nor confined to the Ukraine. It was one -- the last -- of a series of natural famines caused by crop failures that had occurred frequently throughout Russian history and that are familiar in most agricultural societies.
The defendants in the famous "Moscow Show Trials" of 1936, 1937 and 1938 were not framed, but were guilty of at least those crimes to which they confessed.
Leon Trotsky too, an absent codefendant in each of these trials, did conspire with Germany and Japan to overthrow the Soviet government, put an end to the Comintern, and dismember the Soviet Union, and sabotage military defense during wartime, provided he got help to come to power.
The "Great Terror" of mass executions that did indeed take place in the USSR between 1937 and 1938 was an attempt by some Party leaders and the head of the NKVD (secret police) Nikolai Ezhov to sow distrust and discontent among parts of the Soviet population in order to weaken it during an attack and so facilitate the overthrow of the Soviet regime. Stalin and the other Party leaders associated with him opposed this and put an end to it -- when they found out about it.
Stalin tried hard to institute a social-democratic type of democracy in the USSR in the 1930s, and made further attempts during the 1940s, but was opposed and defeated in this by Party leaders.
Nikita Khrushchev's famous attack on Stalin in his "Secret Speech" to the 20th Party Congress in February 1956 is completely dishonest. A careful study of each of Khrushchev's "revelations", or accusations, against Stalin and Lavrentii Beria, shows that every one of them can be proven false in the light of documentary evidence from former Soviet archives.
I could make a much longer list.

In short, nothing we have been told; nothing in the famous "canonical" antisoviet and anti-Stalin books that are routinely cited, is trustworthy.